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Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P168
Surface oxidation of metals using oxygen ion beams
Nikolai Alov 1
1 Lomonosov Moscow State University, 119992 Moscow, Russia
Surface oxidation of Mo, W, Nb and Ta using oxygen ion beams was investigated by Xray
photoelectron spectroscopy (XPS). Irradiation by oxygen ion beams was carried out
at room temperature with ion energy of 1-5 keV, dose of 10 15 -10 18 cm −2 and direction
normal to surface. XPS analysis of oxidized metal surfaces was performed in situ using
Leybold LHS-10 electron spectrometer. The fitted XPS spectra of Mo 3d and W 4f core
levels show that the metal oxidation states 4+, 5+ and 6+ are present in oxide films.
At the initial stage of irradiation the rapid oxidation of Mo and W surface layers was
observed. At higher dose, which depends on the energy of oxygen ions and the kind of
metal, the oxidation of surface layers reaches saturation and the surface composition
remains almost unchanged with increasing irradiation dose. The fitted XPS spectra
of Nb 3d and Ta 4f core levels show that the metal oxidation states 2+, 4+ and 5+
are present in oxide films. At the initial stage of irradiation the rapid oxidation of Nb
and Ta surface layers was observed. However, at higher dose, which depends on the
energy of oxygen ions and the kind of metal, the population of Nb2+, Nb4+, Ta2+ and
Ta4+ reaches a maximum and then begins to decrease. The population of Nb5+ and
Ta5+ continues to increase and the entire oxide films will consist of only Nb5+ and
Ta5+. Using XPS data the absolute values of fundamental parameters of low-energy
oxygen ion interaction with metal surfaces (reaction and sputtering cross-sections) were
calculated.